Aluminium-copper alloys



United States Patent Oflice Patented Sept. 7, 1965 3,205,069 ALUMINIUM-COPPER ALLOYS John Wood, Aylesbury, England, assignor to International Alloys Limited, Aylesbury, England different mechanical properties, that is, a skin much less tough and heavy; consequently, the metal can flow freely in the mould and folds and dross patches are avoided.

Example 1 I No Drawing. Filed Jan. 24, 1962, Ser. No. 168,509 Claims priority, application Great Britain, Jan. 30, 1961, In the casting of cylindrical billets by the continuous 3,503/ 61 casting process from aluminium base alloys containing 4 Claimsin Weight ratios approximately Cu 3%, Mg 0.5%, Sb 0.6%, Sn 0.15%, a considerable percentage up to mventlon relates alulfllmum base alloys $011- 50%--of the production had to be rejected owing to the taming pp together Wlfll elthel m gn formation of folds. The cause of these folds was found magnesium in an amount 1688 than y W g antito be the obstruction presented to the free flow of metal mony and/or bismuth and/ or lithium, and to a method I from the centre of the mould to the wall. An alloy of of preventing the formation of a tough and thick .skin the same composition except for the addition of 0.004% on the molten surface, especially during casting of such by weight Be when cast under identical conditions proalloys. duced billets of which only about 5% had to be rejected In the production of aluminium base alloys contain f01(15- ing copper and some constituents, such as small amounts E p 2 of antlmony for t purpose of unprpvmg .machmablhty Melts of three alloys with compositions as given in the: and strength at high temperatures, dlfiicultles occur due table that follows were prepared, skimmed and kept at to the formatlon 0t a very tough and ra ihlck 750 C. exposed .to still air. To assess the relative tend face 5km on 1lqu1d mfial Whlch lmpedes the free ency towards formation of a tough surface skin qualitaflow of'the sa1d metal 1n the mould and causes drossy i l and quantitative-1y, the exposed f each patches or folds in o ac g to Whether or t 2 melt was hand skimmed six times at 5 minute intervals, the pressure of the liquid metal under this skin is high and finally a seventhtime 1 hour after the first skimming. enough to burst the skin before the surface metal solidi? The visual observationsWhenskimming were noted, and fies. Antimony is generally added in the range of 0.1% the .total weight. 'of jjskimmings. produced determined." and 1% by weight. Theresults were as follows: Y

Nominal composition percent byweight Weight of Alloy N0 skimmings Remarks i Cu Mn Ni Ti Co 21 Sb Be A1 g./10 0 cm 1 1 5 0.25 1.5 0.2 0.3 0.2 Bal. 9.3 Skinbright clean and .collapsible. 2 5 0.25 1. 5. 0.2 0.3 0.2. 0.25 Bal. 21.0 Skin thick- I ,andte- I 113131115. 3 5 0.25 1.5 0.2" 0.3 0.2 0.25 .004 Bal. 14.0 Skin thin clean,

collapsib 1e.' 7

Similar difficulties, generally to a less pronounced The table shows .that the addition of Sb to the Sb free degree, have also been observed in aluminium alloys alloy causes the oxide film to become thick and tenacious, containing copper and additions of bismuth or lithium but that the further addition of Be reduces the thickness in amount 0.03 to 1% and mechanical resistance of the film.

The present invention is concerned with removing or reducing the defects caused by this skin. In accordance Example 3 with the invention this is achieved by the addition of very small amounts of beryllium, of the order of 0.005% by TFStS 5151113? to those fefen'fid to m Q P 2 w weight and in the range 0.002% to less than 0.01% by Famed out with five alloys f Composltlons as glven Weight to a copper containing aluminium base alloy hav- H t table that follows. In this examp the totfll f ing no magnesium constituent or less than 1% by weight of sklmmlngs 111 eafih F was the sklrqmmgs magnesium and containing one or more of the constituefiFcted a v minutenntervals Over Peflod of ents antimony, bismuth and lithium in respect amounts f y t s- Two determinations were made of the above 01% up to 1% f 003% up to 1% f o welght of the SklIIlIIllIlgS in each case, one being for all six skimmings and labelled total in the table, and the 0.03% up to 1% by weight. Copper-containing aluminium base alloys having no magnesium content or less than 1% by weight magnesium and containing antimony and/or bismuth and/ or lithium with beryllium additions in the amounts indicated, form a skin of significantly other being for the five skimmings after the first and labelled standing only in the table, the latter determination thus omitting the first skimming in each case where some part of the skimming may have been dependent on the surface condit on of the metal piece used. (a) copper in an amount about by weight; The results were as follows: (b) manganese in an amount about 0.25% by weight;

Nominal composition of alloy in Skimmings propercout by weight duced in 30 min.

g./100 cm Remarks Alloy N o.

Cu Mg Si Li Bi Be A1 Total Standing only 1 3 0.1 6 Bal. Not 8.3 Clean surface.

determined 2 3 0.1 G 0.1 Del. 33 17.2 Thick.fiufiy skin of oxide. 3 3 0.1 6 0.1 0. 004 Bal. 18 8.6 Fairly clean. 4 3 0.1 6 0.5 Bal. 115 68 Layer ofbrittle dross. 5 3 0. 1 6 0.5 0.007 B211. 133 62 As alloy N0. 4

but thinner layer.

This table shows that the addition of Bi (alloy No. 2) (c) nickel in an amount about 1.5% by weight;

or Li (alloy No. 4) to the alloy free from these elements ((1) titanium in an amount about 0.2% by weight; (alloy No. 1) cause the formation of an oxide skin which i (e) cobalt in an amount about 0.3% by weight;

is thick and fluffy or hard and brittle. The further addi- (f) zirconium in an amount about 0.2% by weight; tion of Be, however, to alloy No. 2 causes changes both (g) antimony in an amount about 0.25% by weight; in the quantity of the dross and in the appearance of the and alloy towards the condition observed as regards alloy (h) beryllium in an amount about 0.004% by weight; No. 1, and as regards alloy No. 4, the further addition of the balance being aluminium.

Be significantly reduces the amount of dross produced. 3. An aluminium base alloy having the characteristic It is known that beryllium and lithium together in low that, during casting thereof a tough and thick skin docs percentages have a protective influence in the case of not form on the molten surface, said alloy being comsurface oxidation of liquid aluminum alloys containing posed of: copper with high additions of magnesium, i.e., more than (a) copper in an amount about 3% by weight; 1% by weight and generally in the order of 5% to 10% 7 (b) magnesium in an amount about 0.1% by weight; by weight, where the oxidation of the liquid metal is very (c) silicon in an amount about 6% by weight; rapid and penetrating. However, it was previously un- (d) bismuth in an amount about 0.1% by weight; and known that beryllium can also prevent the formation of (e) beryllium in an amount about 0.004% by weight; the tough skins formed on aluminium alloys containing the balance being aluminium. copper antimony, bismuth or lithium, but either no mag- 4. An aluminium base alloy having the characteristic nesium or magnesium in amounts less than 1% by weight. that, during casting thereof a tough and thick skin does Aluminium base alloys according to the invention may 40 not form on the molten surface, said alloy being cominclude incidental ingredients where addition is Well posed of: known in the production of aluminium alloys. (21) copper in an amount about 3% by weight;

I claim: (b) magnesium in an amount about 0.1% by weight; 1. An aluminium base alloy having the characteristic (c) silicon in an amount about 6% by weight; that, during casting thereof a tough and thick skin does (d) lithium in an amount about 0.5% by weight; and not form on the molten surface, said alloy being com- (e) beryllium in an amount about 0.007% by weight; posed of: the balance being aluminium. (a) copper in an amount about 3% by weight;

(b) magnesium in an amount about 0.5 by weight; References Cited y the Examine! (c) antimony in an amount about 0.6% by weight; 00 UNITED STATES PATENTS (d) tin in an amount about 0.15% by weight; and (e) beryllium in an amount about 0.004% by weight; 1997494 4/35 Mansfield 138 2,185,348 1/40 Mansfield 75-l38 2 gii zir liiiiiigiiii iuz sg iiiib havin the characteristic 2188203 1/40 Mansfield 75138 X y g 5 2,915,391 12/59 Criner 75-138 X hat, duri ca tin hereo a tough and thick skin does not form on the molten surface, said alloy being com- DAVID L. RECK, Examiner. posed of: 

1. AN ALUMINIUM BASE ALLOY HAVING THE CHARACTERISTIC THAT, DURING CASTING THEREOF A TOUGH AND THICK SKIN DOES NOT FORM ON THE MOLTEN SURFACE, SAID ALLOY BEING COMPOSED OF: (A) COPPER IN ANN AMOUNT ABOUT 3% BY WEIGHT; (B) MAGNESIUM IN AN AMOUNT ABOUT 0.5% BY WEIGHT; (C) ANTIMONY IN AN AMOUNT ABOUT 0.6% BY WEIGHT; (D) TIN IN AN AMOUNT ABOUT 0.15% BY WEIGHT; AND (E) BERYLLIUM IN AN AMOUNT ABOUT 0.004% BY WEIGHT; THE BALANCE BEING ALUMINIUM. 